U.S. patent application number 16/994890 was filed with the patent office on 2020-12-03 for minimum quantity lubrication thread tap.
This patent application is currently assigned to Ford Motor Company. The applicant listed for this patent is Ford Motor Company. Invention is credited to Michael Habel, Ethan Hughey, Shibu Philipose, David Stephenson.
Application Number | 20200376577 16/994890 |
Document ID | / |
Family ID | 1000005019997 |
Filed Date | 2020-12-03 |
United States Patent
Application |
20200376577 |
Kind Code |
A1 |
Habel; Michael ; et
al. |
December 3, 2020 |
MINIMUM QUANTITY LUBRICATION THREAD TAP
Abstract
A thread tap includes a shaft and teeth. The shaft includes
helical passages from the threading end to the base end of the
shaft. Each passage opens through an aperture in the threading end.
A second tap includes a cap and the shaft includes an axially
extending passage. The cap is coupled to the threading end and at
least partially defines apertures in fluid communication with the
passage and the exterior of the tap. A third tap includes teeth
spaced apart by a plurality of linear flutes. The shaft includes a
central passage and a plurality of flute passages. Each flute
passage extends radially outward from a common location in the
central passage to a corresponding one of the flutes. The central
passage is closed to a terminal end of the threading end.
Inventors: |
Habel; Michael; (Ann Arbor,
MI) ; Hughey; Ethan; (Royal Oak, MI) ;
Philipose; Shibu; (Canton, MI) ; Stephenson;
David; (Detroit, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Motor Company |
Dearborn |
MI |
US |
|
|
Assignee: |
Ford Motor Company
Dearborn
MI
|
Family ID: |
1000005019997 |
Appl. No.: |
16/994890 |
Filed: |
August 17, 2020 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
16107116 |
Aug 21, 2018 |
10773323 |
|
|
16994890 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23G 5/06 20130101; B23G
5/005 20130101; B23Q 11/1046 20130101; B23G 2240/12 20130101 |
International
Class: |
B23G 5/00 20060101
B23G005/00; B23G 5/06 20060101 B23G005/06 |
Claims
1. A thread tap comprising: a shaft and a plurality of thread
tapping teeth disposed at a threading end of the shaft, the shaft
including a plurality of passages that extend helically from the
threading end to a base end of the shaft opposite the threading
end, each passage being open through a corresponding aperture
defined by the threading end.
2. The thread tap of claim 1, wherein the corresponding apertures
are equally spaced apart in a circumferential direction about a
central axis of the shaft.
3. The thread tap of claim 1, wherein the corresponding apertures
are defined by a terminal end face of the threading end or a
tapered end face of the threading end.
4. The thread tap of claim 3, wherein the corresponding apertures
are configured to release lubricant in opposite directions from the
terminal end face of the threading end toward the thread tapping
teeth.
5. The thread tap of claim 3, wherein the thread tapping teeth are
disposed axially between the corresponding apertures and the base
end of the shaft.
6. The thread tap of claim 1, wherein the base end of the shaft
includes a manifold chamber in fluid communication with each
passage.
7. The thread tap of claim 1, wherein a helical pitch of the
passages is a different pitch than a thread pitch of the thread
tapping teeth.
8. The thread tap of claim 1, wherein a helical diameter of the
passages is less than a minimum diameter of the thread tapping
teeth.
9. The thread tap of claim 1, wherein the passages are entirely
radially inward of a minimum diameter of the thread tapping
teeth.
10. The thread tap of claim 1, wherein sets of the thread tapping
teeth are spaced apart by flutes defined by the shaft.
11. The thread tap of claim 10, wherein the flutes extend linearly
along the shaft.
12. The thread tap of claim 10, wherein the passages are radially
inward of the flutes.
13. A thread tap comprising: a shaft and thread tapping teeth
spaced apart by a plurality of flutes that extend linearly along a
threading end of the shaft, the shaft including a central passage
and a plurality of flute passages, each flute passage extending
radially outward from a common location in the central passage to a
corresponding one of the flutes, the central passage being closed
to a terminal end of the threading end.
14. The thread tap of claim 13, wherein the common location is a
common axial position along a central axis of the shaft.
15. The thread tap of claim 13, wherein each flute passage is open
to the corresponding flute at a tapered portion of the threading
end.
16. The thread tap of claim 13, wherein the plurality of flute
passages includes a first flute passage and a second flute passage
disposed diametrically opposite the first flute passage.
17. The thread tap of claim 13, wherein the plurality of flutes
consists of a first flute and a second flute, and the plurality of
flute passages consists of a first flute passage and a second flute
passage, wherein the first flute and the second flute extend
linearly along the shaft.
18. The thread tap of claim 13, wherein the central passage
terminating at the common location.
19. The thread tap of claim 13, wherein each flute passage forms an
angle with the central passage of at least 135.degree..
20. The thread tap of claim 13, wherein the first flute passage has
a diameter d.sub.1, the second flute passage has a diameter
d.sub.2, and the central passage has a diameter D.sub.c, wherein
d.sub.1=d.sub.2=D.sub.c/ (2).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S.
application Ser. No. 16/107,116 filed on Aug. 21, 2018. The
disclosure of the above application is incorporated herein by
reference in its entirety.
FIELD
[0002] The present disclosure relates to minimum quantity
lubrication thread tap.
BACKGROUND
[0003] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0004] Conventional thread taps use high volume flow of a liquid
lubricant over the cutting edges of the tool. Some thread taps have
an internal passage that provide this liquid lubricant to each
cutting edge. Since the liquid lubricant is essentially an
incompressible fluid, flow from the passage to each cutting edge
remains substantially based on the pressure of the liquid supplied
to the tool.
[0005] In contrast, minimum quantity lubrication ("MQL") machining
uses lubrication supplied to the cutting edges of a tool through a
lean air-oil mist, rather than through the high volume liquid-based
emulsion in conventional thread tapping. The ratio of air to oil in
the air-oil mist is typically very high and the lubricant mist acts
as a compressible fluid (unlike the incompressible liquid lubricant
of conventional thread tapping). Taps designed for liquid lubricant
flow through internal passages suffer from excessive air
compression and backpressure when used with the air-oil mist of MQL
machining. This can result in wasted lubricant and excess wear on
the tap.
[0006] The present disclosure provides a thread tap having a more
balanced lubrication flow for MQL thread tapping that overcomes the
problems of typical thread taps when used for MQL tapping.
SUMMARY
[0007] In one form, a thread tap includes a shaft and a plurality
of teeth disposed at a threading end of the shaft. The shaft
includes a plurality of passages that extend helically from the
threading end to a base end of the shaft opposite the threading
end. Each passage is open through a corresponding aperture defined
by the threading end.
[0008] According to a further form, the corresponding apertures are
equally spaced apart in a circumferential direction about a central
axis of the shaft.
[0009] According to a further form, the corresponding apertures are
defined by a terminal end face of the threading end or a tapered
end face of the threading end.
[0010] According to a further form, the corresponding apertures are
configured to release lubricant in opposite directions from the
terminal end face of the threading end toward the teeth.
[0011] According to a further form, the base end of the shaft
includes a manifold chamber in fluid communication with each
passage.
[0012] According to a further form, a helical pitch of the passages
is a different pitch than a thread pitch of the teeth.
[0013] According to a further form, a helical diameter of the
passages is less than a minimum diameter of the teeth.
[0014] According to a further form, sets of the teeth are spaced
apart by flutes defined by the shaft.
[0015] According to a further form, the flutes extend linearly
along the shaft.
[0016] According to a further form, the passages are radially
inward of the flutes.
[0017] In another form, a thread tap includes a shaft, a cap, and a
plurality of teeth disposed at a threading end of the shaft. The
shaft includes an axially extending passage open through the
threading end. The cap is coupled to the threading end and at least
partially defines a plurality of apertures in fluid communication
with the passage and an exterior of the thread tap.
[0018] According to a further form, the cap includes a deflecting
body and a plurality of supports. The supports couple the
deflecting body to the threading end. The apertures are disposed
between the supports.
[0019] According to a further form, the plurality of apertures are
equally spaced apart in a circumferential direction about a central
axis of the shaft.
[0020] According to a further form, the cap includes a deflecting
body coaxial with a central axis of the shaft. The deflecting body
narrows in an axial direction toward the passage to direct fluid
from the passage radially outward.
[0021] According to a further form, the cap is mounted to the
shaft.
[0022] According to a further form, the cap is mounted to a
terminal end of the threading end by epoxy, brazing, welding, or
press-fit contact.
[0023] In another form, a thread tap includes a shaft and teeth
spaced apart by a plurality of flutes that extend linearly along a
threading end of the shaft. The shaft includes a central passage
and a plurality of flute passages. Each flute passage extends
radially outward from a common location in the central passage to a
corresponding one of the flutes. The central passage is closed to a
terminal end of the threading end.
[0024] According to a further form, each flute passage is open to
the corresponding flute at a tapered portion of the threading
end.
[0025] According to a further form, the plurality of flutes
consists of a first flute and a second flute. The plurality of
flute passages consists of a first flute passage and a second flute
passage. The first and second flutes extend linearly along the
shaft.
[0026] According to a further form, the first flute passage has a
diameter d1, the second flute passage has a diameter d2, and the
central passage has a diameter Dc, and d.sub.1=d.sub.2=D.sub.c/
(2).
[0027] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the
description and specific examples are intended for purposes of
illustration only and are not intended to limit the scope of the
present disclosure.
DRAWINGS
[0028] In order that the disclosure may be well understood, there
will now be described various forms thereof, given by way of
example, reference being made to the accompanying drawings, in
which:
[0029] FIG. 1 is a perspective view of a thread tap in accordance
with the teachings of the present disclosure;
[0030] FIG. 2 is perspective view of a base end of the thread tap
of FIG. 1;
[0031] FIG. 3 is a side plan view of the thread tap of FIG. 1;
[0032] FIG. 4 is a perspective view of a thread tap of a second
construction in accordance with the teachings of the present
disclosure, illustrating a deflecting cap;
[0033] FIG. 5 is a cross-sectional view of the thread tap of FIG.
4;
[0034] FIG. 6 is a perspective view of a deflecting cap of a second
construction in accordance with the teachings of the present
disclosure;
[0035] FIG. 7 is perspective view of a thread tap of a third
construction in accordance with the teachings of the present
disclosure; and
[0036] FIG. 8 is a cross-sectional view of the thread tap of FIG.
7.
[0037] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present
disclosure in any way.
DETAILED DESCRIPTION
[0038] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses. It should be understood that throughout the drawings,
corresponding reference numerals indicate like or corresponding
parts and features.
[0039] With reference to FIG. 1, a thread tap 10 of a first
construction is illustrated. The tap 10 includes a shaft 14 and a
plurality of external teeth 18. The shaft 14 is disposed coaxially
about a central axis 22 and has a holding portion 26 and a tapping
portion 30 that is axially opposite the holding portion 26. The
shaft 14 defines a plurality of passages 34, 38 that extend in a
helical manner about the central axis 22 through the holding
portion 26 and the tapping portion 30. In the example provided,
there are two passages 34, 38 that maintain separate helical paths
through the holding portion 26 and the tapping portion 30, i.e.,
from a first end 42 of the shaft 14 to a second end 46 of the shaft
14.
[0040] The holding portion 26 is configured to be gripped by a
tapping tool holder (not shown) that can rotate the tap 10 about
the central axis 22. In the example provided, the holding portion
26 has a smooth cylindrical outer surface 50 and a frusto-conical
surface 54 that extends axially from the cylindrical outer surface
50. The frusto-conical surface 54 narrows in the axial direction
toward the first end 42 (i.e., the frusto-conical surface narrows
with increased distance from the tapping portion 30). With
additional reference to FIG. 2, the first end 42 defines a manifold
chamber 58 open through the tip of the frusto-conical surface 54
and in fluid communication with the passages 34, 38. The
frusto-conical surface 54 and/or the cylindrical outer surface 50
are configured to seal with the tool holder (not shown) and the
tool holder is configured to supply lubrication in the form of an
air-oil mist (i.e., minimum quantity lubrication, "MQL") to the
passages 34, 38 via the manifold chamber 58.
[0041] In the example provided, the tapping portion 30 has a
smaller outer diameter than the holding portion 26. The teeth 18
are external teeth disposed about the tapping portion 30 proximate
to the second end 46. The teeth 18 extend helically about the axis
22. In the example provided, the teeth 18 form a single start
thread that winds helically about the tapping portion 30. The teeth
18 have a minor diameter defined by valleys between threadforms and
a major diameter defined by peaks of each threadform.
[0042] With additional reference to FIG. 3, the tapping portion 30
can have a tapered or chamfered region 62 generally between the
teeth 18 and the second end 46. In the example provided, the first
few teeth 18 proximate to the second end 46 can also be within the
chamfered region 62 such that the first few teeth 18 are chamfered
threadforms. The chamfered region 62 narrows toward the second end
46. In the example provided, the chamfered region 62 narrows to a
diameter that is less than the minor diameter of the teeth 18.
[0043] The passages 34, 38 have a pitch (i.e., the distance along
the axis 22 that the helix takes to make one complete revolution
about the axis 22) that is different than the pitch of the teeth
18. In the example provided, the passages 34, 38 have a helical
pitch that is significantly less than the pitch of the teeth 18,
such as a helix pitch of between 15.degree. and 30.degree., though
other configurations can be used. In the example provided, the
passages 34, 38 have a constant helix radius (i.e., a constant
helix diameter). In other words, the passages 34, 38 maintain a
constant distance apart from the axis 22 throughout the shaft 14.
The helix diameter is less than the minor diameter of the teeth 18
such that the passages 34, 38 remain completely radially inward of
the teeth 18. In the example provided, the minor diameter of the
teeth 18 is between 5 mm and 14 mm, though other sizes can be used
depending on the size of the hole (not shown) to be tapped and the
size of threads desired.
[0044] The passages 34, 38 can be equally spaced apart in the
circumferential direction. In the example provided, the two
passages 34, 38 are diametrically opposite each other. Each passage
34, 38 is open through the tapping portion 30 at a corresponding
aperture 66. In the example provided, the chamfered region 62
narrows to a diameter that is less than the helix diameter so that
the apertures 66 are open through the chamfered region 62 to
provide lubrication at the chamfered region 62. In the example
provided, the apertures 66 are diametrically opposite each other so
that rotation of the tap 10 causes the lubrication to be expelled
from the passages 34, 38 in opposite directions radially outward
from the end face toward the teeth 18.
[0045] In an alternative configuration, not specifically shown, the
chamfered region 62 does not narrow less than the helix diameter
and the apertures 66 are open through the terminal end face of the
second end 46. In this alternative example, rotation of the tap 10
causes the lubrication to be expelled from the passages 34, 38 in
opposite directions radially outward toward the teeth 18.
[0046] Returning to the example provided, the tap 10 is a forming
tap and does not include any flutes or leading cutting edges. While
not specifically shown, the forming tap can include oil grooves
extending axially along the shaft 14 through the peaks of the teeth
18, i.e., locations where the threadforms of the teeth 18 have been
truncated without forming cutting edges. The apertures 66 can be
aligned in the circumferential direction with corresponding ones of
the oil grooves (not shown) to emit lubrication directly or
indirectly to the grooves (not shown).
[0047] In an alternative configuration, not specifically shown, the
tap 10 can be a cutting tap including a plurality of flutes and
leading cutting edges at each flute. In this alternative
configuration, the apertures 66 can be aligned in the
circumferential direction with corresponding ones of the flutes
(not shown) to emit lubrication directly or indirectly to the
flutes (not shown).
[0048] With reference to FIGS. 4-6, a thread tap 410 of a second
construction is illustrated. The tap 410 includes a shaft 414, a
plurality of external teeth 418, and a cap 422. The shaft 414 is
disposed coaxially about a central axis 426 and has a holding
portion 430 and a tapping portion 434 that is axially opposite the
holding portion 430. The shaft 414 defines a central passage or
bore 438 that extends coaxially along the central axis 426 through
the holding portion 430 and the tapping portion 434. The bore 438
is open through a first end 442 of the shaft 414 and extends fully
through the shaft 414 to be open through an opposite second end
446.
[0049] The holding portion 430 is configured to be gripped by a
tapping tool holder (not shown) that can rotate the tap 410 about
the central axis 426. In the example provided, the holding portion
430 has a smooth cylindrical outer surface 450. In the example
provided, the outer surface 450 is configured to seal with the tool
holder (not shown) and the tool holder is configured to supply
lubrication in the form of an air-oil mist (i.e., minimum quantity
lubrication, "MQL") to the bore 438 through the first end 442.
[0050] In the example provided, the tapping portion 434 has a
smaller outer diameter than the holding portion 430. The teeth 418
are external teeth disposed about the tapping portion 434 proximate
to the second end 446. The teeth 418 extend helically about the
axis 426. In the example provided, the teeth 418 form a single
start thread that winds helically about the tapping portion 434.
The teeth 418 have a minor diameter defined by valleys between
threadforms and a major diameter defined by peaks of each
threadform.
[0051] The tapping portion 434 can have a tapered or chamfered
region 454 generally between the teeth 418 and the second end 446.
In the example provided, the first few teeth 418 proximate to the
second end 446 can also be within the chamfered region 454 such
that the first few teeth 418 are chamfered threadforms. The
chamfered region 454 narrows toward the second end 446. In one
configuration, the chamfered region 454 can narrow to a diameter
that can be less than the minor diameter of the teeth 418, though
other configurations can be used.
[0052] The cap 422 is fixedly (i.e., non-movably) mounted to the
second end 446 and is generally configured to deflect MQL flow from
the bore 438 radially outward toward the teeth 418. In the example
provided, the cap 422 includes a deflector body 458 and a plurality
of supports 462. The deflector body 458 has a shape configured to
direct lubrication flow from the bore 438 radially outward. In the
example provided, the deflector body 458 has a generally conical
shape coaxial with the axis 426. The base of the conical deflector
body 458 is spaced axially apart from the second end 446 and the
deflector body 458 narrows toward its tip proximate to the second
end 446. In the example provided, the tip of the conical deflector
body 458 extends within the bore 438, though other configurations
can be used. While illustrated in FIG. 5 as a generally conical
shape, other shapes can be used, e.g., a pyramid, a frusto-conical
shape, or a curved surface (e.g., as shown in FIG. 6).
[0053] The supports 462 are radially outward of the bore 438 and
extend from the base of the deflector body 458 in the axial
direction toward the second end 446. The supports are fixedly
attached to the tapping portion 434. The supports 462 are spaced
apart in the circumferential direction to define apertures or
openings between the supports 462. In the example provided, there
are four supports 462 equally spaced apart to define four openings,
though other numbers of supports 462 can be used. In the example
provided, the second end 446 defines four mounting recesses 466
that correspond to the four supports 462. Each recess 466 is open
through the terminal face of the second end 446 and disposed
radially outward of the bore 438. Each support 462 is received in a
corresponding one of the recesses 466 and fixed therein. In the
example provided, the supports 462 are press-fit in the recesses
466.
[0054] In an alternative configuration, not specifically shown, the
supports can be adhered within the recesses 466, such as with an
epoxy for example. In another alternative configuration, not
specifically shown, the supports 462 can be welded or brazed in the
recesses 466 or to the second end 446 absent the recesses 466.
[0055] Returning to FIGS. 4 and 5, the cap 422 is disposed entirely
radially inward of the chamfered region 454 and radially inward of
the minor diameter of the teeth 418. In the example provided, the
cap 422 can be made of a material that is softer than the shaft 414
since the cap 422 does not contact the workpiece (not shown) during
tapping. For example, the cap 422 may be made from plastic, powder
metal, or low carbon steel. Accordingly, the cap 422 can be made
using an inexpensive process, such as injection molding,
blanking/forging, or sintering for example.
[0056] In the example provided, the tap 410 is a forming tap and
does not include any flutes or leading cutting edges. In the
example provided, the forming tap can include oil grooves 470
extending axially along the shaft 414 through the peaks of the
teeth 418, i.e., locations where the threadforms of the teeth 418
have been truncated without forming cutting edges. The openings
between the supports 462 can be aligned in the circumferential
direction with corresponding ones of the oil grooves 470 to emit
lubrication toward the grooves 470. In an alternative
configuration, the tap 410 can be configured without the oil
grooves 470.
[0057] In an alternative configuration, not specifically shown, the
tap 410 can be a cutting tap including a plurality of flutes and
leading cutting edges at each flute. In this alternative
configuration, the openings between the supports 462 can be aligned
in the circumferential direction with corresponding ones of the
flutes (not shown) to emit lubrication directly or indirectly to
the flutes (not shown).
[0058] With reference to FIG. 6, an alternative configuration of
the cap is illustrated and indicated with reference numeral 422'.
The cap 422' is similar to the cap 422 (FIGS. 4 and 5), except as
otherwise shown or described herein. Elements denoted by primed
reference numerals are similar to the elements shown and described
in FIGS. 4 and 5 having similar non-primed numerals, except as
otherwise shown or described herein.
[0059] Instead of a conical shape, the deflector body 458' has a
curved, concave surface 610 that directs the lubrication radially
outward. The concave surface 610 is axisymmetrically curved with a
central peak 614 at the axis 426 and a variable radius of curvature
that increases with radial distance from the axis 426 to a base
618. In the example provided, the curvature is generally parabolic
in shape, though other configurations can be used. In one
configuration, the radius of curvature at the center is between 2
and 4 times the tap major diameter and increases by roughly a
factor of two or the major diameter with increased radial distance
from the axis 426. In the example provided, the deflector body 458'
can optionally have directing features such as recesses, valleys or
channels 622 configured to improve MQL delivery radially outward to
the teeth 418 (FIGS. 4 and 5), especially when the tap 410 rotates
at high speeds (i.e., high revolutions per minute). The channels
622 can cause the deflector body 458' to act as a centrifuge or
centrifugal pump, e.g., increasing centrifugal force acting on the
MQL mixture to whip the MQL mixture radially outward toward the
teeth 418 (FIGS. 4 and 5). The channels 622 can optionally spiral
about the axis 426 depending on the rotational direction of the
teeth 418 (FIGS. 4 and 5) and thus the rotational direction of the
tap 410 (FIGS. 4 and 5). In the example provided, the channels
spiral in a clockwise manner from the central peak 614 to the base
618. In an alternative configuration, not specifically shown, the
channels 622 can spiral in a counter-clockwise direction from the
peak 614 to the base 618. In another alternative configuration, not
specifically shown, protrusions (e.g., fins) can protrude from the
concave surface 610 to direct the flow. The protrusions (not shown)
can spiral about the axis 426 similar to the channels 622.
[0060] With reference to FIGS. 7 and 8, a thread tap 710 of a third
construction is illustrated. The tap 710 includes a shaft 714 and a
plurality of external teeth 718. The shaft 714 is disposed
coaxially about a central axis 722 and has a holding portion 726
and a tapping portion 730 that is opposite the holding portion 726.
The shaft 714 defines a central passage or bore 734 and a plurality
of branch passages or bores 738. The central bore 734 extends
coaxially along the central axis 722 through the holding portion
726 and a region of the tapping portion 730. The bore 734 is open
through a first end 742 of the shaft 714 at the holding portion 726
and extends through the shaft 714 toward an opposite second end
746, but is not open through the second end 746.
[0061] The holding portion 726 is configured to be gripped by a
tapping tool holder (not shown) that can rotate the tap 710 about
the central axis 722. In the example provided, the holding portion
726 has a smooth cylindrical outer surface 750. In the example
provided, the outer surface 750 is configured to seal with the tool
holder (not shown) and the tool holder is configured to supply
lubrication in the form of an air-oil mist (i.e., minimum quantity
lubrication, "MQL") to the bore 734 through the first end 742.
[0062] In the example provided, the tapping portion 730 has a
smaller outer diameter than the holding portion 726. The teeth 718
are external teeth disposed about the tapping portion 730 proximate
to the second end 746. The teeth 718 extend helically about the
axis 722. In the example provided, the teeth 718 form a single
start thread that winds helically about the tapping portion 730.
The teeth 718 have a minor diameter defined by valleys between
threadforms and a major diameter defined by peaks of each
threadform.
[0063] The tapping portion 730 can have a tapered or chamfered
region 754 generally between the teeth 718 and the second end 746.
In the example provided, the first few teeth 718 proximate to the
second end 746 can also be within the chamfered region 754 such
that the first few teeth 718 are chamfered threadforms. The
chamfered region 754 narrows toward the second end 746. In one
configuration, the chamfered region 754 can narrow to a diameter
that can be less than the minor diameter of the teeth 718, though
other configurations can be used.
[0064] In the example provided the tapping portion 730 includes a
pair of grooves or channels 758 that are diametrically opposite
each other and open in the direction radially outward relative to
the axis 722. The channels 758 extend linearly from the second end
746, toward the first end 742, through the teeth 718, and terminate
axially between the teeth 718 and the holding portion 726. In the
example provided, the channels 758 have troughs that are radially
inward of the minor diameter of the teeth 718, though other
configurations can be used. In the example provided, the tap 710 is
a forming tap and the channels 758 are oil grooves, such that the
teeth 718 do not have cutting edges at their interface with the
channels 758. In an alternative configuration, not specifically
shown, the tap 710 can be a cutting tap and the channels 758 can be
flutes such that the teeth 718 have leading cutting edges at each
flute.
[0065] The branch bores 738 extend from a terminal end of the
central bore 734 at an angle such that the branch bores 738 extend
radially outward and axially toward the second end 746. The branch
bores 738 intersect the central bore 734 at a common location that
is axially positioned within the region of the tapping portion 730
that includes the teeth 718 so that the branch bores 738 are in
fluid communication with the central bore 734. The branch bores 738
are straight and form an obtuse angle 762 with the central bore
734. The branch bores 738 are open through the tapping portion 730
to provide lubrication to the teeth 718 via apertures 766.
[0066] In the example provided there are two branch bores 738 that
are diametrically opposite each other and aligned with the channels
758. The apertures 766 are disposed within the channels 758 to
provide lubrication directly to the channels 758. In the example
provided, the angle 762 formed by the branch bores 738 is at least
135.degree. and the angle 762 can be greater than 150.degree.
depending on the length of the tapping portion 730. In the example
provided, the branch bores 738 open to the channels 758 at a
location within the chamfered region 754. In an alternative
configuration, not specifically shown, the branch bores 738 can
open to the channels 758 at a location not in the chamfered region
754, i.e., being open in the same axial region of the channels 758
where the teeth 718 would have their full major diameter. In the
example provided, the branch bores 738 each have a diameter that is
equal to the diameter of the central bore 734 times the square root
of two. In other words, d.sub.1=d.sub.2=D.sub.c/ (2), where d.sub.1
and d.sub.2 are the diameters of the branch bores 738 and D.sub.c
is the diameter of the central bore 734. This ratio of diameters
provides an equalized area for flow of the lubrication.
[0067] In an alternative configuration, not specifically shown, the
central bore 734 extends fully through the second end 746, but is
plugged by a plug (not shown). The plug (not shown) seals the
central bore 734 at the second end 746 to prevent lubrication from
exiting through the second end 746. The plug (not shown) terminates
within the central bore before the intersection of the branch bores
738 with the central bore 734 so as not to inhibit flow from the
central bore 734 to the branch bores 738. The plug (not shown) can
be attached within the central bore 734 with any suitable manner,
e.g., welded, brazed, adhesive, epoxy, or threaded into the central
bore 734.
[0068] The description of the disclosure is merely exemplary in
nature and, thus, variations that do not depart from the substance
of the disclosure are intended to be within the scope of the
disclosure. Such variations are not to be regarded as a departure
from the spirit and scope of the disclosure.
* * * * *